1. Field of the Invention
The present invention relates to a process for the preparation of carboxymethyl cellulose ether alkali metal salts (or alkali metal cellulose glycolates; herinafter referred to as "CMC"). The CMC according to this invention possesses an improved flow property in aqueous solutions thereof and is especially suitable for use in printing pastes.
2. Description of the Prior Art
CMC as a synthetic paste possesses excellent properties such as a thickening property, a suspension-stabilizing property and a film-forming property, and it is widely used in the fiber industry, the food processing industry, the paint industry, the construction material industry, the cosmetic industry, the ceramic industry, the pharmaceutical industry and the agricultural industry, and in drilling muds used in the boring of oil wells and the like. By virtue of its following advantageous properties, CMC is widely used as an ingredient of pasty printing color paste:
1. The CMC paste has little or no reducing property, and therefore, it does not damage the coloring property of a dye and it manifests a good color-reproducing property. PA1 2. The dried film has good physical properties and has a good water retension property, and therefore, run-away is much reduced during the steaming step. PA1 3. The paste can be easily removed by washing after the dyeing step. PA1 4. A stock paste or a dyeing paste can easily be prepared, and the paste has a good compatibility with other pastes. PA1 5. The paste has a high plastic flowability and the past hardly penetrates into the back of the cloth to which it is applied.
In order to have good effects on factors influencing the printing, such as silk-screening, operation, such as the squeeze-parting property, the doctor-parting property, the screen-passing property, the level dyeing and the sharpness of the printed pattern, a printing paste is required to have a moderate plastic flowability. CMC has a relatively high plasticity and is suitable for hand printing such as stencil printing. On the other hand, a printing paste having a high Newtonian flowability is preferred for machine printing such as roller printing and auto-screen printing.
The water medium method for preparing CMC has been practiced for many years, but in this method, the ratio of effective utilization of the etherifying agent (the ratio of (a) the amount of the etherifying agent that becomes bonded to the cellulose, to (b) the amount of the etherifying agent initially charged) is low. As a means for overcoming this disadvantage, a solvent method was proposed by Hayakawa et al (see Japanese patent publication No. 7349/57) as a method characterized by a high effective utilization ratio of monochloroacetic acid used as etherifying agent. In this method, the amount of the solvent is from 2 to 10 times the amount of the cellulose. Watanabe et al proposed a method in which an organic solvent is used in an amount at least 30 times the weight of the cellulose (Kogyo Kagaku Zasshi, 68, 83, 1590 (1965). In this method, a high effective utilization ratio of monochloroacetic acid can be attained, but it is difficult to obtain CMC having a high sliding property.
It is said that the flow characteristics of CMC are generally influenced by the distribution of the substituents introduced by the etherification, and in the above solvent method, attempts have been made to obtain improved flow characteristics by increasing the amount of the alkali added and increasing the degree of substitution. However, in these attempts, the ratio of the amount used of the alkali is increased and the effective utilization ratio of the monochloroacetic acid is reduced, and therefore, the economical advantage inherent in the solvent method is lost.
From experience it was found that the flow characteristics, namely the viscosity characteristics, of CMC are influenced by the manufacturing conditions, but according to conventional techniques, conditions providing CMC having viscosity characteristics satisfying all the requirements of a printing paste have not yet been achieved.